SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78b423741e4781fdab1a9590665dced34ce74fc69bbb48e2a981f410208a1153' 
  AND token = '5ZcWawacqsvKzh/dy4tveU+dyMtKrYgYtDjF5jR+2GM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}